Catalytic chemical heater



Nov. 20, 1962 c. B. MOORE ETAL CATALYTIC CHEMICAL HEATER Filed April 23, 1959 IN VEN TORS' THOMAS M. AMUNDSON DICK MOORE ATTORNEY WILLARD K. CHARLES 8.

3,064,902 Patented Nov. 20, 1962 Free 3,064,262 CATALYTIC CHEMECAL HEATER Charles B. Moore, Cambridge, Mass, Thomas M. Amundson, Turlock, Calif, and Willard K. Dick, Water-town, N.Y., assignors to General Mills, Inc., a corporation of Delaware Filed Apr. 23, 1959, Ser. No. 808,504 12 Claims. (Cl. 237-33) This invention relates to a method for heating compartments or spaces and a device for heating the same. More particularly, this invention relates to heaters of the class wherein heat is evolved by the catalytic decomposition of a liquid.

While this invention is applicable to heating any room, compartment or space, the same will be illustrated in connection with heating aircraft and particularly for heating the gondola of manned or unmanned higher altitude research balloons which will serve as an illustration but not as a limitation of this invention.

Among the important features of this invention is the structure of the metering valve which is self purging and embodies a flexible seal permanently secured to the valve control lever and valve block thereby preventing leakage or sticking of the moving parts of the valve over a wide range of ambient conditions. Another feature of this invention is the reaction vessel which is provided with heat exchange means to reduce the temperature thereof making possible a reduction in weight and size of the heater. Still another feature of this invention is the provision for discharging liquid exhaust products formed in the heater into the outside atmosphere intermittently whereby freezing of this liquid around the exhaust nozzle is avoided.

It has previously been shown that compartments or spaces in aircraft may be heated by carrying out a continuous exothermic chemical reaction within a vessel and conducting the heated reaction products through a tube lining the walls of the compartment. While a number of exothermically reactive substances may be used for supplying heat energy, one chemical reaction which has been used for this purpose is the catalytic decomposition of hydrogen peroxide to form oxygen gas and steam with an associated liberation of heat. Hydrogen peroxide is a preferred exothermically reactive substance because, among other things, it requires no oxidizer, can be handled with relative safety, and serves as an effective source of heat energy.

In prior art heaters of the class described, it has been a problem to provide safe and reliable control over the introduction of exothermically reactive substance into the reaction chamber. The valves used heretofore for this purpose have been subject to an occasional malfunctioning which is usually due either to sticking of parts in extreme heat or cold or to foreign material obstructing the valve. It is thus one object of this 'invention to provide a catalytic chemical heater characterized by accurate and reliable temperature regulation through the use of an improved valve and valve control mechanism for metering the exothermically reactive substance.

In the prior art of heating by the catalytic decomposition of hydrogen peroxide, it has been the accepted practice to carry out the reaction at a high temperature in a vessel which is especially designed to operate in intense heat. The requirement that the vessel resist extreme heat has made the reaction vessel undesirably heavy and bulky. In aircraft of any sort, it is of paramount importance that the weight of auxiliary equipment be kept to a minimum. As distinguished from the prior art, it is an object of this invention to maintain the reaction vessel at a relatively low temperature, whereby the heater can be reduced in size and weight but yet will provide the same total heat output as prior art heaters.

In order to reduce the weight of the aircraft during the time it is aloft, it is desirable to expel the reaction products produced by the heater into the outside atmosphere. When the water or water vapor formed in the reaction is expelled, it will freeze very rapidly as it comes in contact with the frigid outside environment. Thus, there will be a tendency for the water component of the exhaust to freeze around the exhaust outlet, causing a plug of ice to obstruct the flow of water and gas therethrough which can result eventually either in a rupture of this outlet pipe or the opening of a safety valve which will place the heater out of commission. It is thus another object of this invention to prevent water formed by the heater from freezing around the outlet used to discharge the reaction products into outside environment.

The above mentioned general objects of this invention, together with others inherent in the same, are attained by the devices illustrated in the accompanying drawings and description, throughout which like refer ence numerals indicate like parts:

FIGURE 1 is a semidiagrammatic vertical section of one embodiment of this invention.

FIGURE 2 is a plan view of the fuel storage tank and a portion of the repressurizing pipe.

FIGURE 3 is a schematic Wiring diagram of the perature regulating circuit.

Referring now to the figures, there is shown a storage tank 10 adapted to contain a supply of an exothermically reactive liquid which will decompose under the influence of a catalyst. The preferred exothermically reactive liquid for use in this invention is concentrated hydrogen peroxide. The liquid contained in tank 10 passes by gravity through a line 12 communicating with tank 10 through a suitable coupling 11. Liquid passing .downwardly through line 12 enters valve block 114 through an inlet port 16 located at the bottom of block 14. Line 12 may .be connected to port 16 by any suitable coupling v18.

Within valve block 14 is provided a cylindrical needle chamber 20 communicating with inlet port 16. Slideably mounted within needle chamber 20 is a generally cylindrical needle 22 to control the flow of liquid from the tank 10 into reaction vessel 24. When the valve mechanism is assembled, the needle 22 is placed in valve block 14 through port .25 which is then sealed by plug 27. Flag 27 may be removed to provide access for cleaning the needle chamber 20.

The needle 22 is provided at one end with a cylindrical extension 26 having a conical tip 28 adapted to project into and control the flow of liquid through an orifice 30 leading from inlet port 16 to needle chamber 20. The upper edge of orifice 30 comprises a circular valve seat 32 adapted to coact with the conical tip 28 of the needle. Orifice 30 is made smaller in diameter than any of the lines used for conveying the exothermically reactive liquid so that it will limit. the flow of the liquid through the valve during the time needle 22 is out of contact with valve seat 32.

The provision for line contact between the needle 22 and the valve seat .32 together with the rapid upward flow of liquid over the valve seat was found to virtually eliminate the opportunity for foreign material .to lodge on the valve seat, a condition which could prevent the valve from seating properly. The valve may, therefore, be thought of as self purging.

To control the position of needle 22 a valve lever 34 is provided, one end of which projects through an openteming 35 drilled in needle 22 at right angles to the axis thereof. The other end of valve lever 34 extends out of the valve block 14 through a passage 36 which passes through the wall of the valve block and communicates with needle chamber 20. The valve lever 34 is pivotally mounted within hole 38 in the center of a fulcrum disc 40 which is fixed telescopically in passage 36. The upper and lower sides of hole 38 are tapered to form sharp edges about which valve lever 34 may pivot.

Covering the outwardly projecting end of valve lever 34 is a flexible plastic sheath 44 which may be made of polyethylene or the like. The sheath 44 is closed around the free end of valve lever 34 and is provided with a flange 46 at the other end which lies adjacent fulcrum disc 40. A retaining ring 48 is used to secure the fulcrum disc 40 and flange 46 to the wall of the valve block 14 thereby sealing passage 36 against leakage. Retaining ring 48 may be conveniently fastened to valve block 14 by screws 50.

The valve lever 34 and needle 22 are positioned by means of an electromagnetic valve actuator 52 comprising a frame 54 secured to valve block 14 in any suitable manner, an electromagnet 56 mounted on frame 54 and an armature 58 made of magnetic material which i pivotally attached to frame 54. The armature 58 is connected to the free end of the sheath 44 by a suitable fastener 59 which transmits the motion thereof to the valve lever 34 and needle 22. When a current passes into electromagnet 56 through wires 60 and 62, the armature 58 is drawn downwardly thereby moving needle 22 ofi its seat 32 and allowing liquid to pass through the valve. When the current is interrupted, a spring 64 attached to armature 58 returns the armature, valve lever and needle to their original positions. The control of the electromagnetic valve actuator 52 will be explained more fully hereinbelow.

A great advantage in the valve construction described derives from the fact that the needle may be positioned without any direct mechanical connection between the valve lever 34 and the control means outside the valve. The provision for sealing the valve lever 34 completely within the flexible sheath 44 absolutely prevents leakage of liquid out of the valve as will occur, for example, around the valve control lever of a conventional valve in which there is sliding contact between the valve control lever and the sealing element or stufiing. Furthermore, since there is no sliding contact between valve lever 34 and the sealing element, the opportunity for the valve to stick or jam during operation is avoided.

Liquid passing through orifice 30 into valve chamber 20 leaves the valve block 14 through port 66 and then passes through pipe 68 which is connected at one end to port 66 and at the other end to the reaction vessel 24. Within pipe 68 there is provided a nipple 69 having a small orifice 71 in the center thereof to prevent surging of liquid.

The reaction vessel includes an inner cylindrical tank 70 filled from the end nearest the connection to pipe 63 to approximately its center with a plurality of circular catalyst screens 72 and an outer heat exchange jacket 74 welded to and enclosing the major part of tank 70. The

outer surface of heat exchange jacket 74 is covered withv a suitable heat insulating material 76 such as molded asbestos. The catalyst screens 72 together make up a catalyst bed 78 and may be secured in position by lock ring 80 which is held in a circumferential groove 82 located on the inside wall of tank 70. The lower end of tank 70 is closed so that liquid passing into the reaction vessel from pipe 68 flows upwardly through the catalyst bed 78 which serves to decompose the liquid and cause the liberation of heat.

Hydrogen peroxide may be decomposed catalytically to form water and oxygen by the action of certain cations such as copper, vanadium, nickel or silver. If hydrogen peroxide is used as the exothermically reactive liquid, a preferred catalyst is silver wire woven to form a screen and coated with a rare earth metal such as samarium. If a different fuel is used, some other catalyst may be employed.

The reaction products formed during the decomposition of the liquid pass out of tank 70 through port 82 at the top or tank 70 and into pipe 84 secured to port 82. The other end of pipe 84 is secured to a T coupling 86. Connected to one outlet of T coupling 86 is a heat radiator pipe 88 and connected to the other outlet is a repressurizing pipe 90 which leads to the storage tank for the purpose of repressurizing the space within the tank 10 as liquid is withdrawn therefrom.

The repressurizing pipe 90 is fastened to the top of the storage tank 10 by a suitable coupling 92. A segment of the repressurizing pipe 90 close to coupling 92 makes a 360 loop 94 in a horizontal plane above the tank 10. The loop 94 is greater in diameter than the diameter of tank 14) and serves to prevent the escape of liquid through pipe in the event the tank or the entire aircraft is turned on its side. In the repressurizing pipe 90 is provided a pressure safety valve 96 which includes a frangible metal disc set to rupture when a predetermined pressure is reached within the line.

From T coupling 86 the hot reaction products pass through heat radiator pipe 88 including a heat transfer section 98 illustrated diagrammatically as a coil to radiate heat from the hot gases passing therethrough to the compartment to be heated. The heat transfer section 98 of pipe 88 may lead back and forth along the inside surface of the wall of the compartment. After passing through pipe 88, the reaction products which have now been cooled considerably enter the heat exchange jacket 74 through port 100 and circulate around tank 70 so as to cool the wall thereof and be reheated thereby. It is desirable that at least part of the steam passing through pipe 88 is condensed to water since considerably more heat can be withdrawn from tank 70 if the water entering jacket 74 undergoes a change from the liquid phase to the gaseous phase when it contacts the Wall of tank 70. By thus lowering the temperature of tank 70, it was found that the reaction vessel 24 may be reduced considerably in size and weight and may be constructed of a light weight metal such as aluminum which would otherwise melt from the heat evolved during the decomposition of the liquid. The decomposition temperature of concentrated hydrogen peroxide is about 1100 F.

The reaction products which have been reheated (and revaporized if necessary) by contact with tank 70, leave the heat exchange jacket 74 through port 102 and then pass through pipe 104. Pipe 104 include a second heat radiation section 106 illustrated diagrammatically as a coil which may be attached to the inside wall of the compartment in the same manner as pipe 88. During passage through pipe 104, heat is radiated from the reaction products to the compartment. The outlet end of pipe 104 is connected to the exhaust discharge unit 108 which expels the reaction products into the atmosphere.

The exhaust discharge unit 108 includes a tubular housing 110 closed at the upper end by a circular plate 112 secured thereto by bolts 114, an inlet port 116 in the center of end plate 112 to which pipe 104 is attached, a funnel shaped exhaust nozzle 117 opening into the atmos phere located at the bottom of the housing 110, a wate1 reservoir 118 mounted concentrically within the housing and a water outlet duct 120 extending from the inside of the water reservoir 118 through the bottom wall 122 thereof to approximately the top of the exhaust nozzle 117. The exhaust discharge unit 108 is secured to the floor of the gondola 123 by means of flange welded to the wall of housing 110. Between the bottom of he housing 110 and the nozzle 117 there is provided a sponge rubber sealing ring 127.

Integral with the top of the outlet duct 120 is a cup shaped extension 124 enclosing duct 120 and approximately concentric therewith. Extension 124 communi cates with the inside of duct 120 through a port 126. The free end of extension 124 is spaced from the bottom wall of water reservoir 118 so that water in the reservoir is able to pass up through cup shaped extension 124, through port 126, and then through outlet duct 120. The bottom end of outlet duct 120 is preferably cut at an angle to its axis to help prevent drops of water from accumulating around the outlet end thereof. Outlet duct 120 may be secured to water reservoir 118 by any suitable means such as a nut 128.

The top of the water reservoir 118 is provided with a plurality of vents 130 which allow the gaseous reaction products to flow continuously from inlet port 116 around the outside of the water reservoir and into the atmosphere through the exhaust nozzle 117. During operation, the gaseous reaction products will pass out through the ex haust nozzle 117 continuously, as explained, while the liquid portion of the exhaust will be expelled intermittently since liquid will be retained in the water reservoir 118 until the level of port 126 is reached, at which time the reservoir will be emptied through outlet duct 120 by a siphoning action. The filling and emptying cycle will repeat throughout operation of the heater.

By expelling the water formed by the decomposition of the liquid intermittently, it was found that freezing of the water around the outlet duct was greatly minimized, so that blocking of the outlet was virtually eliminated. This result is, of course, highly desirable since a plug of ice obstructing the exhaust outlet will cause a pressure build-up in the liner and result in either the rupture of the line or the opening of a safety valve.

Referring now especially to FIGURES 1 and 3, there is shown a circuit including three thermally regulated switches 132, 133 and 134 of the type which will open when its temperature exceeds a certain predetermined level. Switch 132 is attached to heat radiation pipe 88 at a point adjacent T coupling 86, switch 133 is attached to the heat transfer section 98 of pipe 88 and switch 134 is attached to the heat transfer section 106 of pipe 104. Switch 132 is a safety switch which remains closed at normal operating temperatures and is set to open when a predetermined maximum temperature is reached in pipe 38. Switches 133 and 134 are set to open at a somewhat lower temperature than switch 132, i.e. whenever the temperature at the heating coils falls below a desired predetermined minimum. Switches 133 and 134 are wired in parallel and are both connected in series with switch 132 and with electromagnetic valve actuator 52. Current is supplied by battery 136.

When the heater is put in operation, current passes from battery 136 through switches 133 and 134, through switch 132 and completes the circuit through electromagnetic valve actuator 52, which maintains needle 22 in the open position. When the temperature at coils 9'8 and 1% reaches a predetermined level, either switches 133 or 134 may open. If both switches 133 and 134 are open simultaneously the current will be interrupted and the liquid valve will close. If the temperature of pipe 88 ever exceeds a predetermined safe limit, switch 132 will open cutting off the current and thus closing the liquid valve.

Before the tank is filled with hydrogen peroxide, the tank and lines should be thoroughly cleaned or passivated by a suitable chemical treatment or by other means to remove impurities that might catalyze decomposition of the liquid therein. Means to accomplish this end will be apparent to those skilled in the art.

The materials used in the construction of the heater must, of course, have no tendency to catalyze undesired reaction of the exothermically reactive liquid. When hydrogen peroxide is used as the exothermically reactive liquid, the lines, heat radiation pipes, lock ring 80 and needle 22 may be made of stainless steel while the storage tank, valve block 14, reaction vessel, heat exchange jacket and exhaust discharge unit may be made of appropriate aluminum alloys. The exhaust nozzle may be made of molded plastic. Both the outlet duct 12!) and the exhaust nozzle may be coated with a water repellent film such as silicone resin or the like to aid in preventing water and ice from accumulating thereon.

In view of the principles set forth herein, we have shown some of the ways of carrying out the present invention and some of the equivalents which are suggested by these disclosures.

We claim:

1. In a heater of the class wherein heat is evolved by the catalytic decomposition of an exothermically reactive liquid adapted to form gases and vapors when reacted, means for storing a supply of said liquid, a reaction vessel for catalytic decomposition of said liquid, means for regulating the flow of said liquid into said reaction vessel, means for transferring sufiicient heat from the reaction products formed by the decomposition of said liquid to a space to be heated so that at least some of said reaction products are condensed to the liquid state, and means for intermittently expelling the liquefied reaction products into the atmosphere.

2,. A heater according to claim 1 wherein said reaction vessel is at least partially enclosed within a hollow heat exchange jacket, said heat exchange jacket including means for passing a cooling medium therethrough.

3. A heater according to claim 2 wherein the means for passing a cooling medium through said heat exchange jacket comprises a pipe to convey said reaction products into said jacket after said reaction products have cooled.

4. A heater according to claim 1 wherein the means for intermittently expelling the liquid portion of said reaction products into the atmosphere comprises a reservoir and a siphoning duct operatively associated with said reservoir to empty said reservoir after the liquid therein has risen to a predetermined level.

5. In a space heater, a container for storing a supply of an exothermically reactive substance, a reaction chamber, means for conducting said substance from said container to said reaction chamber, a catalyst bed within said reaction chamber to decompose said substance exothenrnically, a radiator connected to the outlet of said reaction chamber to transfer heat from the reaction products formed by the decomposition of said substance to a space to be heated, means responsive to the temperature of said radiator for controlling the rate at which said substance is introduced to said reaction chamber and means for intermittently discharging liquid reaction products into the environment outside the space to be heated whereby the formation of ice around said discharge means thereof is avoided.

6. A method of heating aircraft comprising metering into a reaction vessel an exothermically reactive substance which forms reaction products, a portion of which is gaseous and a portion of which is condensed to a liquid during the heating operation, decomposing said substance catalytically, conducting the hot reaction products formed by the decomposition of said substance through a radiator to heat said aircraft and at least partially cool said reaction products, thereafter conducting the reaction products over the outside wall of said reaction vessel to withdraw further heat therefrom expelling said gaseous products from the system, storing said liquid reaction products in a reservoir and expelling said liquid reaction products through an exhaust outlet into the atmosphere outside said aircraft intermittently whereby the formation of ice around the exhaust outlet is avoided.

7. A method of heating which comprises catalytically decomposing in a walled reaction vessel an exothermically reactive substance which forms reaction products, a portion of which is gaseous and a portion of which is condensed to a liquid during the heating operation, extracting heat from said reaction products formed by such decomposition and thereby at least partially cooling said reaction products, thereafter conducting the reaction products into heat-exchange relationship with said reaction vessel and thereby withdrawing further heat from the vessel while reheating said products, and then extracting further heat from said reheated reaction products sufficient to condense a substantial amount of said reaction products to a liquid state.

8. The method according to claim 7 wherein said liquid portion is collected in a reservoir and intermittently expelled from said reservoir and wherein said gaseous portion is expelled from the system continuously.

9. A method of heating aircraft comprising metering into a reaction vessel an exothermically reactive substance which forms reaction products, a portion of which is condensed to a liquid during the heating operation, catalytically decomposing said substance in said vessel, Withdrawing heat from the hot reaction products from said catalytic decomposition to heat said aircraft, collecting said liquid portion of said reaction product in a temporary storage reservoir, and intermittently expelling said liquid reaction product into atmosphere outside said aircraft.

'10. In a heater of the class wherein heat is evolved by catalytic decomposition of an exothermically reactive liquid, storage means for storing a supply of said liquid, a reaction vessel, a supply conduit between said storage means and said reaction vessel, means for regulating the flow of said liquid from said storage means through said supply conduit to said vessel, heat exchange means connected to receive the products from said reaction vessel, and a repressurizing line connecting said reaction vessel and said storage means above the normal liquid level in said vessel and storage means, said repressurizing line including a loop portion of a greater diameter than the width of said storage means, said loop being disposed in a horizontal plane when said storage means is in an upright position, said loop thereby preventing gravity flow of liquid from said storage means through the repressurizing line to the reaction vessel when the storage means is tipped substantially from its upright position.

11. In a heater of the class wherein heat is evolved by catalytic decomposition of an exothermically reactive liquid, storage means for storing a supply of said liquid, a reaction vessel, 2. supply conduit between said storage means and said reaction vessel, means for regulating the fiow of said liquid from said storage means through said supply conduit to said vessel, heat exchange means connected to receive the products from said reaction vessel, and a repressurizing line connecting said reaction vessel and said storage means above the normal liquid level in said vessel and storage means, said repressurizing line including a safety valve for opening said line in case excessive pressures build up in one of said reaction vessel, repressurizing line and storage means.

12. A heater of the class wherein heat is evolved by catalytic decomposition of an exothermically reactive liquid comprising a reaction vessel having an outer wall with a heat exchange jacket, valve means controlling the supply of said liquid to said reaction vessel, first radiator means connected to receive the output from said reaction vessel, connecting means between said radiator and said heat exchange jacket for conducting the cooled reaction product from said radiator to said jacket, second radiator means connected to said jacket for receiving the reheated reaction products conducted from said first radiator through said jacket, first heat responsive control means connected to said valve means and located in heat responsive relationship to the reaction products moving from said reaction vessel to said first radiator means and operatively connected for shutting off said fuel supply in response to a predetermined maximum safe temperature of said reaction products, and second heat responsive control means, also connected to said valve means and associated with one of said radiator means for opening said valve means and supplying said liquid to said reaction chamber in response to predetermined minimum temperature at said radiator means.

References Cited in the file of this patent UNITED STATES PATENTS 707,478 White Aug. 19, 1902 1,281,056 Nash Oct. 8, 1918 1,943,053 Roisset Jan. 9, 1934 2,321,940 Robertson June 15, 1943 2,375,834 Walker May 15, 1945 2,414,828 McCollum Jan. 28, 1947 2,428,078 Heymann Sept. 30, 1947 2,551,823 'Buttner et al. May 8, 1951 2,579,023 Thomas Dec, 18, 1951 2,810,434 Bramming Oct. 22, 1957 2,926,492 Flanagan Mar. 1, 1960 

1. IN A HEATER OF THE CLASS WHEREIN HEAT IS EVOLVED BY THE CATALYTIC DECOMPOSITION OF AN EXOTHERMICALLY REACTIVE LIQUID ADAPTED TO FORM GASES AND VAPORS WHEN REACTED MEANS FOR STORING A SUPPLY OF SAID LIQUID, A REACTION VESSEL FOR CATALYTIC DECOMPOSITION OF SAID LIQUID, MEANS FOR REGULATING THE FLOW OF SAID LIQUID INTO SAID REACTION VESSEL, MEANS FOR TRANSFERRING SUFFICIENT HEAT FROM THE REACTION PRODUCTS FORMED BY THE DECOMPOSITION SAID LIQUID TO A SPACE TO BE HEATED SO THAT AT LEAST SOME OF SAID REACTION 